This invention is directed to a divided flow self-leveling system for vehicles utilizing hydraulic cylinders, a telescopic lifting hoist, arm or boom, and a material handling attachment or carriage. Typically, a high lift loader, exemplified by Frederick et al. U.S. Pat. No. 4,147,263, has an elongated telescopic boom pivotally secured at one end to a vehicle, and a carriage such as a fork lift pivotally secured to the opposite end of the boom. An hydraulic cylinder is used to raise and lower the boom relative to the vehicle and another hydraulic cylinder is used to tilt the carriage relative to the boom. Such vehicles are in common use for building construction and similar purposes.
Because the attitude of the carriage changes as the boom is raised or lowered on its pivot connection to the vehicle, constant adjustment of the flow of fluid to the hydraulic cylinder operating the carriage is necessary to maintain the desired level load carrying position of the carriage. Current methods for maintaining the desired relative positioning of the boom and carriage include mechanical parallelogram systems or mechanical-master/hydraulic-slave loop systems. However, use of these systems is not always possible nor practical.
The principal object of the present invention, therefore, is to provide a universally applicable system to automatically maintain any desired attitude of the material handling carriage attachment relative to the lifting or hoisting boom. In addition, an override feature is provided to allow independent adjustments.